Structural Anatomy

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/30455

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The Influence of Ecogeographic Variation in Human Nasal Morphology on Thermal Conditioning of Inspired Air
(2021) Thai, Elizabeth; Amaranayaka, Hasintha; Patil, Sandeep; Yokley, Todd; Dennis, Brian; Maddux, Scott D.
Most air conditioning of inspired air occurs in the nasal passages and is largely dependent on external environments. Studies show strong associations between climate and ecogeographic patterning of human nasal morphology. Individuals indigenous to cold-dry environments exhibit relatively longer/taller/narrower nasal passages than individuals from hot-humid climates, and these morphologies are assumed to reflect functional differences. To test these associations between nasal morphology and air-conditioning function, we assessed cranial CT scans of 2 individuals"—one of European ancestry (EA) and one of West African ancestry (WA). 3D models of nasal passages were created using 3D Slicer software and were artificially dilated in-silico to simulate fully decongested nasal passages prior to collecting morphometric measurements, mucosal surface area (SA), and airway volume (AV). 3D models of each individual were then employed in Computational Fluid Dynamics (CFD) simulations, via ANSYS fluent software, to assess differences in intranasal airflow heat and moisture transfer. Ambient air conditions were set at -5°C, 35% relative humidity. As expected, the EA individual exhibited longer/taller/narrower nasal passages compared to the WA individual. The EA individual exhibited higher mucosal SA and lower AV resulting in a higher surface-area-to-volume (SA/V) ratio compared to the WA individual. Our CFD simulations also followed theoretical predictions. The higher SA/V ratio of the EA individual resulted in increased heat transfer compared to the WA individual. The results of our study provide support for assertions that ecogeographic variation in human nasal passages reflects climate-mediated evolutionary demands for intranasal air-conditioning.
Muscular Asymmetries in Anatomical Donors with Lower-Limb Amputations
(2021) Finco, Malaka; Kim, Suhhyun; Menegaz, Rachel A.
Purpose: Muscle atrophy from amputation has been associated with increased gait asymmetry, fall risk, and overuse injuries. This study investigated between-limb muscular differences in donors with lower-limb amputations to determine if findings reflect living individuals. We hypothesized each donor's most compromised limb would show less muscle mass, lower pennation angle and PCSA, and fewer and smaller type 1 fibers compared to their most intact limb. Methods: Two male unembalmed donors 61-67 years of age with diabetic lower-limb amputations were obtained through the UNTHSC Willed Body Program. Four muscles were dissected from each limb: gluteus maximus, sartorius, rectus femoris, and biceps femoris long head. PCSA was calculated using the following formula: [(muscle mass x cos(pennation angle)] / [fiber length x muscle density (1.067 g/cm-3)]. Histological (H&E) staining of muscle tissue determined fiber density and cross-sectional area. Immunohistochemical (IHC) staining identified the percentage of fibers containing the fast isoform of myosin heavy chain (MHC), or type 2 "fast-twitch" fibers. Results: Biceps femoris PCSA was 18.1-68.6% larger on each donor's most compromised limb compared to their most intact limb. Histological staining also showed smaller cross-sectional biceps femoris muscle fibers on the most compromised side compared to the most intact side. IHC analyses of fiber phenotype in these muscles are ongoing. Conclusion: Knowledge of muscle adaptations following amputation in donors can confirm accurate biomechanical modeling and inform rehabilitation techniques to reduce muscle atrophy.
Anatomical Variation in a Deep Back Muscle and Possible Implications
(2021) Floyd, Jillian; Meehan, Grace; Park, Clair; Riggs, Alison; Hayes, Olivia; Fisher, Cara
Background: The longissimus thoracis muscle is a part of the erector spinae muscle group, originating from the thoracolumbar fascia, and inserting onto the transverse processes of the first through twelfth thoracic spinevertebrae. The multifidus muscle originates from the posterior superior iliac spine (PSIS) and inserts into on the spinous processes; . iIt is involved in extension and stabilization of the vertebrae in localized movements. Dysfunctions of these muscles are often associated with low back pain, a common complaint among U.S. patients. Case Presentation: This case study describes a novel anatomical variation in the musculature of the deep back discovered during a routine dissection of a 72-year-old female cadaver. The variation identified in this subject is located unilaterally on the right side, from the PSIS, and ends at the transverse process of the third lumbar spinevertebrae. Conclusions: Based on our literature review, we have concluded that the variation is an atypical deep back muscle. Future studies could examine the effects of these variants, and their implication, in somatic and physiological dysfunctions, such as scoliosis.
Tibialis Anterior and The Bridle Procedure
(2021) Cronk, Jacob; Fisher, Cara
Background: The Bridle procedure is a surgical intervention for the treatment of foot drop due to common fibular nerve damage. It involves the transfer of the tibialis posterior tendon through the interosseus membrane and anastomosis to the tendons of the tibialis anterior and fibularis longus muscles. Case Information: A 54-year-old Caucasian male cadaver presented with abnormal anatomy of the tibialis anterior muscle. Dissection revealed a bifurcation of the tibialis anterior tendon at the level of the superior extensor retinaculum with one part of the tendon continuing to its normal insertion on the medial cuneiform and 1st metatarsal and the other part inserting on the lateral aspect of the cuboid. Further dissection revealed sutures at the point of insertion on the cuboid indicating that surgical fixation had been performed and that this was not an anatomical variation. It was subsequently identified as a "Bridle procedure." Atypically, both tibialis posterior and fibularis longus tendons remained attached to their typical insertions, while the tibialis anterior tendon was split longitudinally. The free part of the tibialis anterior was fixed to the cuboid rather than joined with the fibularis longus tendon. The authors suspect a modified version of the Bridle procedure, but identifying the specific name may be difficult given a limited medical history. Conclusions: This cadaveric case study illustrates a unique presentation of the reconstructed anatomy of a surgical procedure used in the treatment of foot drop or steppage gait pathologies.
Bilateral Enlarged Testes: A Case Report
(2021) Spore, Paul; Ly, Connie; Mathews, Joel; West, Lauren; Fisher, Cara
Background: The major components of the male reproductive system consist of the penis, scrotum, testes, and the epididymis. The testicles begin in the abdominal cavity in the fetus and descend through the processus vaginalis in the abdominal wall. If the processus vaginalis remains patent after birth, this can predispose a person to indirect inguinal hernias of the intestine. Case Information: During a routine cadaver dissection, a 76-year old male presented with bilateral enlarged testes, both nearly five times the size of an average male testis. Removal of the outer layers of the scrotum revealed solidified green, yellow, and grayish purulent exudate surrounding both testes between the layers of the parietal and visceral tunica vaginalis. The presentation of both testes differed greatly. The left testis was easily compressible and had a large varicocele, while the right testis was turgid and contained a large hematoma. The inferior pole of the left testis had extensive fibrous scarring and epididymal-testis junction and the anterior surface of left testis had two small nodules protruding from the tunica albuginea. In addition to the findings within the reproductive system, an indirect inguinal hernia was identified within the right spermatic cord. Conclusion: We believe the cause of the bilateral enlarged testes were from two different sources rather than a single disease or incident, due to the stark differences between the two. This case report attempts to further the understanding of the causes of enlarged testes and the relationship between gastrointestinal and reproductive disorders.
Bilateral Absent Fibular (Peroneal) Arteries
(2021) Ali, Arkoon; Thomas, Alexander; Faught, Cassidy; Vedantam, Rahul
Background: The most common branching pattern in the lower extremity is the popliteal artery branching into the anterior tibial artery and tibiofibular trunk. The documentation of aplastic fibular artery is quite rare in the scientific literary world and is mostly found incidentally in unrelated procedures. The absence of a fibular artery can lead to compensatory changes in the posterior tibial artery. Case Presentation: The bilateral absent fibular arteries described in this case report were found in a 75-year old female during routine cadaver dissection at The University of North Texas Health Science Center. The donor had no known complications from this anatomical variation and died from unrelated causes. In this case, the popliteal artery is seen branching into the anterior and then posterior tibial arteries. There is no formation of the tibiofibular trunk nor the fibular artery. The posterior tibial artery supplies the gastrocnemius and other muscles of the posterior compartment of the leg. In addition, the posterior tibial artery fills the role of the absent fibular artery by sending compensatory branches to the lateral compartment of the leg to supply fibularis longus, brevis, and lateral foot. These unique branches from the posterior tibial artery allow for blood supply to the lateral lower extremity and lateral foot musculature. This variation was found bilaterally in the cadaver. Conclusion: This case illustrates a unique presentation of a cadaver with an unusual anatomic variant: bilateral missing fibular arteries.
Anatomic relationships in a set of thoracopagus twins
(2021) Dickerson, Austin; Fisher, Cara
Background: Conjoined twins occur from aberrant embryogenesis, at an estimated incidence of 1 in 200,000 births, with many being stillborn. There are many subtypes of conjoined twins, with their classifications based on anatomical relationships between the two individuals. Similarly, twin survival to birth and potential for surgical separation are based largely on anatomy, especially organ sharing. In the field of pediatric surgery, advances have been made in the understanding of this unique condition and the factors that affect twin survival. This case details the specific anatomy of a set of conjoined female twins. Case Information: Detailed dissection of female conjoined twins reveals unique anatomic relationships and organ sharing between the two. The twins are thoracopagus, or joined at the thorax. Each twin has a separate head and a separate pair of upper and lower extremities. There are distinct, separate abdomens and pelves. The twins share a heart, diaphragm, and liver. Each has separate sets of lungs, and separate foregut, midgut, and hindgut structures. Conclusions: Medical and surgical management of conjoined twins depends largely on the highly variable anatomy and the resulting impacts on physiology. This case report details a set of thoracopagus twins and their unique anatomy. The twins share a heart, which occurs in nearly all thoracopagus twins, and is rarely compatible with life. While the medical history of the twins described here is unknown, a detailed dissection of this well-preserved specimen and exploration of anatomic relationships adds to the current literature and understanding of this unique condition.
External Fixation vs Plaster Splintage in Maintaining Reduction of PER Stage 3 Ankle Fracture Dislocations; A Cadaveric Study
(2021) Inglima, Vincent; Peine, Weston; Motley, Travis; Checketts, Rees
Purpose: Unstable bimalleolar ankle fractures are a common injury. Typical initial treatment involves closed reduction with splinting. Occasionally the ankle is so unstable that external fixation is used to provide increased stability to the reduced ankle. In such cases the patient is subjected to additional anesthesia risks and pin site infections. Our study assesses the biomechanical difference between stabilization modalities. Our null hypothesis is that external fixation does not provide increased stability compared to plaster splintage in treatment of Pronation External Rotation (PER) type 3 fractures. Methods: Using 7 cadaveric limbs we simulated PER stage 3 bimalleolar ankle fractures and applied plaster splintage or delta frame style external fixation to the fracture-dislocations. A pronatory/external rotation force was applied to the splinted ankles until the talus was dislocated (defined as greater than 50% displaced of the talus relative to the tibia). The stabilization modality was then removed and the process was repeated using the alternative method of stability on each limb. Results: The mean load to failure in the splintage group was 14 lbs. while the external fixation group had a load to failure of 10.14 lbs (p-value = .03). There was no significant difference in load to failure between plaster being applied first to the limbs (p-value = .83) nor if external fixation was applied first (p-value = .67) Conclusions: From our results we can conclude that plaster splintage provided greater stability than delta frame style external fixation in maintaining PER ankle fractures post reduction.
Sexual Dimorphism Within Dental Microstructure
(2021) Aldeeb, Sara; Handler, Emma
Purpose: A general pattern of sexual dimorphism is displayed across humans. Many males generally have a larger body than females. This dynamic has also been demonstrated within the oral cavity. For example, on average, many males have larger teeth than females. However, despite clear gross dental size differences, some studies have suggested that males and females also exhibit divergent quantities of enamel. This study aims to contribute to the growing body of evidence suggesting sexual dimorphism exists in the microstructure of human dentition. Moreover, this study will develop a protocol for sectioning human dentition in order to quantify enamel and dentin volumes using computerized tomography (CT) scans. Methods: Skeletal CT scans from adult subjects were loaded onto 3D slicer; a 3D visualization software. The CT scans were digitally segmented to measure volumetric areas of dental microstructure within each tooth bilaterally. Results: Measurable differences are present in gross dental size and quantities of dental microstructure between sexes. Preliminary data has demonstrated that males exhibit less relative enamel compared to females. A protocol for sectioning human dentition in order to quantify microstructure volumes utilizing CT scans was also generated. Conclusion: Sexual dimorphism exists not only in the size of human teeth but also within their enamel substrate. This protocol will aid future studies in a guided protocol to continue to grow evidence of sexual dimorphism within the oral cavity.
A Case of An Accessory Levator Scapulae Muscle
(2021) Mong, Joy; Wagner, Lianne; Fisher, Cara
Background: The levator scapulae is a posterior axioappendicular muscle that attaches the upper limb to the vertebral column. It originates from C1-C4 transverse processes and inserts on the margin of the superomedial angle of the scapula. This case report documents a variation of the musculature in the levator scapulae with a unilateral accessory muscle inserting into the trapezius instead of the scapula. There have been some documented cases of anatomical variations of levator scapulae, however these variations were usually found to be of atypical origin or insertion. There have not been any documented cases of an accessory levator scapulae muscle belly matching the morphology noted here. The clinical implications of anatomical variants such as this one must be considered. Case Information: During a detailed cadaver dissection, a left unilateral accessory muscle of the levator scapulae was discovered. It originated just anterior to the bulk of the levator scapulae at the C2 level and inserted into the superior descending trapezius. This accessory levator scapulae measured 6.5 cm long and 0.5 cm wide. Conclusion: Knowledge of anatomical variants of levator scapulae is relevant to clinicians working in the fields of surgery, neurology, radiology and musculoskeletal medicine. This muscle is frequently implicated in the etiopathology of neck and shoulder pain and increased tension in levator scapulae has also been linked to increased cervicogenic headaches. Structural variations, such as this, may be a contributing factor to postural abnormalities leading to chronic myofascial pain and headaches.
Plantaris Tendon Insertion Variant
(2021) Spore, Paul; Fisher, Cara
Background: The plantaris muscle is thought to be a vestigial muscle and its tendon lies between the gastrocnemius and soleus muscles. It is most common for the plantaris tendon to insert onto the medial calcaneal tuberosity or onto the calcaneal tendon. The plantaris muscle and tendon insertion are thought to possibly play a role in calcaneal tendinopathy. Although it does not play a significant role in foot plantarflexion, it could possibly play a role in proprioception for the muscles that surround it. Case Information: Dissection of the posterior compartment of the left leg of a - year old embalmed female revealed a rare variation in muscular anatomy. The plantaris tendon inserted into the transverse inter-muscular septum between the tibia and the calcaneal tendon. The literature review revealed that this insertion point occurs approximately 3% of the time. Conclusion: While this variation in insertion is documented, it is the least common of the 5 types of plantaris tendon insertions. This case report attempts to further the understanding of the variance of plantaris tendon insertion points and how they can impact diagnosis and treatment of calcaneal tendinopathy.
The Risk Factors and Causes Associated with Ectopic Pregnancies
(2021) Vats, Pulkit; Hannay, Nathan
An ectopic pregnancy occurs when the fertilized egg implants in an improper location. Fertilization normally occurs in the uterine tube. Following zygote formation, the fertilized egg then travels to the superior part of the uterus and implants into the endometrium where it can receive proper nutrients and blood supply. This implantation however can occur elsewhere, most commonly the uterine tube, and results in the fetus receiving improper nutrients, ultimately leading to death of the zygote. This process is known as ectopic pregnancy, specifically tubal pregnancy. There are many factors associated with ectopic pregnancies, including hormonal imbalances, fallopian tube inflammation, abnormal development of the fertilized egg, and smoking (Mayo Clinic). Ectopic pregnancies can be specifically harmful when gone unnoticed. If this condition is not recognized and treated promptly, the fallopian tube can rupture and cause fatal consequences. Further research is prompted to further understand the correlation that exists between pathologies found in a donor cadaver, including a history of smoking, cirrhosis, uterine fibroids, and cancers in the lungs, tongue, and skin.
Craniofacial Bone Mineral Density During Growth in Mice with Osteogenesis Imperfecta (OI)
(2021) Miller, Courtney; Wright, Tommy; McBride, Alexandra H.; Organ, Jason; Menegaz, Rachel A.
Purpose: Osteogenesis imperfecta(OI) is a genetic connective tissue defect resulting in fragile bones due to mutations affecting formation of type I collagen. Low bone mineral density (BMD) in the post-cranial skeleton has been reported in human patients and murine models with OI, yet little is known about craniofacial biomineralization in the disorder. Typically, skeletal mineralization is responsive to the strain environment. The aim of this study is to investigate longitudinal changes in craniofacial BMD in a mouse model of OI type III (most severe form), and to quantify BMD in regions relative to feeding biomechanical forces. Methods: Homozygous recessive OI murine (OIM), a mouse strain with a COL1A2 mutation modeling OI type III, and unaffected wild-type (WT) littermates were micro-CT scanned at weeks 4, 10, and 16. BMD in eight regions was analyzed using Bruker CTAnalyzer software and Mann-Whitney U tests. Results: OIM mice had significantly (p< 0.05) lower BMD than WT mice in all eight regions during week 4, no significant differences in week 10, and significant differences at the parietal bone, mandibular symphysis, and maxillary incisor regions during week 16. Absolute BMD was higher within regions proximal to the bite point at skeletal maturity. Conclusions: These results support a trend that OIM mice have lower BMD in the craniofacial skeleton compared to WT mice throughout growth and BDM in all mice is affected by proximity to bite forces. Understanding craniofacial mineralization patterns in OI could assist in the implementation of pharmaceutical interventions to increase BMD.
Anatomical Mapping of the Posterior Interosseous Nerve and Artery
(2021) Penfield, Monica; Penfield, Monica; Bell, Richard
Purpose: To determine variation of where the posterior interosseous artery (PIA) and nerve (PIN) converge in the distal, posterior aspect of the forearm. Methods: At the UNTHSC anatomy lab, 10 cadavers (five men and five women) were selected and dissected. The merging of the PIN and PIA was revealed in the left and right forearms for each cadaver. A digital caliper was used to measure from the middle point between the olecranon process and lateral epicondyle to the location of where the structures meet in the forearm. These measurements were then converted to average thumb interphalangeal joint (IPJ) widths (based on previous research). Results: The data collected from the ten cadavers indicate that the PIN and PIA converge, on average, 91.492 mm (9.1492 cm, about 4.5 thumb IPJ widths) down the length of the forearm. The variation between the left and right upper extremities within each cadaver ranged from 0 mm to 8.667 mm. Conclusion: The results provide a valuable clinic resource for medical professionals attempting to provide effective manual intervention or modalities to relieve the symptoms of PIA or PIN entrapment within the posterior forearm. The clinician can use an average of 4.5 thumb IPJ widths to measure distally down the forearm to identify the approximate convergence location of the PIA and PIN structures.
INVESTIGATING ECOGEOGRAPHIC VARIATION IN SUPERIOR AND FUNCTIONAL ETHMOIDAL BREADTH IN INTERNAL AIRWAY DIMENSIONS
(2021) Grace, Caroline; Maddux, Scott D.; Schaefer, Cecelia
Superior Ethmoidal Breadth (SEB = maximum breadth between the left and right frontoethmoidal sutures) is widely employed as a proxy for internal nasal airway dimensions. SEB is also commonly argued to evince climatic adaption in modern humans, as populations living in cold-dry environments predictably exhibit narrower SEB dimensions than those inhabiting tropical environments. However, as SEB anatomically spans the upper nasal airways (common and superior meatuses) and the ethmoid air cells, the accuracy of SEB as a proxy for airway dimensions remains questionable. Here, we evaluate the correlation between SEB and internal airway dimensions using linear measurements collected on CT scans from a mixed-sex sample of human crania (n=217) ancestrally derived from sub-Saharan Africa, Europe, East Asia, and the Arctic Circle. Our results demonstrate SEB is highly correlated (r=0.807, p< 0.0001) with functional airway breadth (FEB), suggesting SEB is a reliable proxy. ANOVA results indicate, in addition to significant differences in SEB (F=36.5, p< 0.0001), regional differences exist for common (F=3.95, p=0.009) and superior (F=3.19, p=0.024) meatus breadths and ethmoid air cell breadth (F=9.01, p< 0.0001). Specifically, the African-derived sample consistently exhibit the widest nasal dimensions and the Arctic-derived sample the narrowest dimensions. Our results indicate a positive scaling relationship between SEB and internal airway breadths, with the wider SEB values of the African-derived sample actually underestimating their disproportionately wider common and superior meatuses. Cumulatively, these results empirically support use of SEB as proxy for upper nasal airway breadth.
Assessing Ecogeographic Variation in the Nasal Passages Utilizing 3D Semilandmarks
(2021) Higgs, Lyndee; Maddux, Scott D.; Thai, Elizabeth
Purpose: Prior research has shown strong statistical relationships between geographically-patterned variation in nasal skeletal morphology and global climatic conditions. Specifically, the nasal skeletons of individuals indigenous to cold-dry environments tend to be longer, taller, and especially narrower, than those from hot-humid environments. As the nose heats and humidifies inspired air, this morphological patterning is believed to reflect the specific air-conditioning demands of different climates. However, while it is widely assumed the morphology of the nasal skeleton accurately reflects that of the functional (soft-tissue) nasal passages, the existence of ecogeographic variation in the three-dimensional (3D) nasal soft tissues has yet to be empirically demonstrated. Thus, this study investigates 3D shape variation in decongested soft-tissue nasal passages of individuals of European (EA) and African (AA) descent (n=15). Methods: Using 3D Slicer and Avizo, a total of 260 semi-landmarks were collected from the decongested nasal passages of each individual. General Procrustes Analysis (GPA) was then used to align the semilandmark configurations and a Principal Component Analysis (PCA) was subsequently performed using the Geomorph package in R. Results: PC1 (20.2%) largely contrasts EA individuals with positive PC1 scores (relatively narrower nasal passages) from AA individuals with negative PC1 scores (relatively wider nasal passages). Conclusions: These results generally conform to morphological expectations, suggesting a concordance between skeletal and decongested soft-tissue nasal anatomy. This study thus provides the impetus for future research investigating the relationship between variation in nasal soft-tissue anatomy and air-conditioning physiology.
Localizing the Course of the Radial Nerve Based on Anatomical Landmarks: A Cadaveric Study
(2021) Barnes, Kalan; Powell, Jake; Beck, Cameron; Skinner, Matthew; Pientka II, William; Fisher, Cara
Purpose: Iatrogenic radial nerve injury during the posterior approach to the humerus is a well-documented complication. The aim of this study is to define the course and variability of the radial nerve along the posterior humerus in relationship to the medial and lateral epicondyles. Methods: With the cadaver in a lateral position, the shoulder and elbow were flexed to 90 degrees and supported as done intraoperatively. The epicondyles of the humerus were aligned and tensioned to be held parallel to the operating table. The forearm was clamped in neutral to the supporting pipe. A posterior incision was made over the humerus to expose the triceps muscle. Dissection was continued to the bone and exposure of the radial nerve was completed with care. The location where the radial nerve intersected the medial and lateral edges of the humerus was marked. Images, with a ruler placed on the humerus, were taken of the posterior arm from a standard camera setup. ImageJ was utilized to measure the distance from the epicondyles to where the radial nerve crossed the humerus. Results: Measurements are currently being performed and analyzed in arms of 25 cadavers. Conclusion: Identification of the radial nerve allows for protection of the nerve during a posterior surgical approach to the humerus. This study allows for simple guidelines for orthopedic surgeons to identify the radial nerve and limit iatrogenic injury.
Anterior Interosseous Syndrome: A Case Study in a Seventy-one-Year-Old Women with Multiple Nerve compressions
(2021) Shakibai, Nasim
Background: Anterior interosseous nerve (AIN) syndrome is rare and accounts for less than 1% of all upper extremity neuropathies. AIN syndrome can be due to trauma, compression of the nerve, or neuritis.Case Information: A 71-year-old woman presented with numbness and tingling in the right thumb, index, middle and part of the ring finger. She had difficulty flexing her index finger and thumb. Nerve study demonstrated carpal tunnel syndrome, and right ulnar nerve dysfunction without motor involvement. On exam, there was thenar atrophy and tenderness over the proximal median nerve. She had a positive Tinel's and Phalen sign of the wrist; and positive Tinel's sign in the proximal border of the pronator teres and the ulnar nerve at the cubital tunnel. She had 0/5 strength in the flexor pollicis longus and flexor digitorum profundus of the index finger, and weakness with flexor digitorum superficialis flexion. She was not able to make an O sign. During surgery, an ulnar nerve decompression and carpal tunnel release were performed. During the proximal median nerve release, an anomalous intramuscular tendon near the early portion of the AIN nerve was found and divided.Conclusion: In the elbow and the forearm, the median nerve can be compressed by the lacertus fibrosus, heads of the pronator muscle, and anomalous structures such as the ligament of Struthers and Gantzer muscle. Patients will present with only motor weakness and will not be able to flex their interphalangeal joint of the thumb and distal interphalangeal joint of the index finger.
Multiple Lateral Cervical Musculature Variation: A Case Report
(2021) Wagner, Lianne; Mong, Joy; Fisher, Cara
Background: The paired anterior, middle, and posterior scalene muscles are found in the lateral neck. The anterior scalene originates from the transverse processes (TPs) of C3-C6 and inserts on the first rib. The middle scalene originates from the TPs of C2-C7 and also inserts on the first rib. The posterior scalene originates from the TPs of C5-C7 and inserts on the second rib. The levator scapulae also attaches to the cervical TPs, typically originating from C1-C4 and inserting on the angle of the scapula. This case report documents multiple anatomical variations of the scalenes and levator scapulae in the lateral neck. While there have been case studies on other scalene variations, there are no documented cases matching the morphologies noted here. Case Information: Detailed dissection revealed multiple muscle variations. The first, an accessory middle scalene muscle with two bellies. The superior belly originates at C1-C5 TPs, running in an inferomedial fashion, anterior to the middle scalene. The inferior belly runs in an inferior fashion, anterior to the middle scalene, with some fibers inserting on the middle scalene and the remainder merging with the first intercostal fibers. The second, an accessory levator scapulae muscle, with two bellies coming off the 3rd belly of levator scapulae and attaching to C5. The final variation, the posterior scalene muscle attaching to the first rib instead of the second. Conclusion: Some possible clinical implications of this variant include cervicogenic headaches, thoracic outlet syndrome, and compression of the brachial plexus.
Aberrant Extensor Digitorum Tendon Lies Superficial to Extensor Retinaculum
(2021) Son, Benjamin; Evans, Zachary; Paez-Espinoza, Monserrat; Brevell, Bailey; Fisher, Cara
BACKGROUND: The extensor digitorum muscle (EDM) is located on the posterior aspect of the forearm. The tendons of this muscle typically run deep to the extensor retinaculum (ER), which is a fibrous sheath that stabilizes and aligns the extensor tendons. ER has been used in the past as a graft source to treat Boxer's Knuckle, an injury of the metacarpophalangeal (MP) joint capsule. This indicates the minor role ER plays in physiologic function. EDM is innervated by the posterior interosseous nerve, a branch of the radial nerve, and is used in extending digits 2 through 5. CASE INFORMATION: This case report presents an anatomical variance that was found within a 66-year-old male cadaver's EDM. The most medial tendon of the extensor digitorum lies superficial to the extensor retinaculum. We have theorized that this anatomical variance would present itself in a similar manner as the palmaris longus tendon. CONCLUSION: To our knowledge, this anatomic variation has yet to be documented. The donor's medical history reports no motor dysfunction to the phalanges, thus it has been concluded that this variation contributed to no complications. The lack of previous documentation on this variant, both in scientific literature and the donor's personal medical history, leads us to suspect that the variant is either uncommon or not of mechanical significance.

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